Lithiation characteristics of a complex oxide containing V(V) and Cu(II), Cu11V6O26, were investigated. Lithiation was carried out chemically using an n-BuLi/hexane solution. The valence states of copper and vanadium and the structural changes upon lithiation were analyzed using ESR, XRD and IR measurements. It was revealed that reduction processes occurred consecutively with an increasing extent of lithiation, x=Li/(11Cu+6V). Up to x=3, Cu(II) was reduced preferentially to Cu(I) in the single phase. At 3<x, V(V) was reduced to V(IV) parallel to the reduction of Cu(II) in the two phase system, and the second phase was amorphous in nature. Further Cu(O) was formed at 7 < x, and at 14 < x the mother oxide disappeared. The open-circuit potentials of lithiated Cu11V6O26 were 3.4 to 3.0 V at < x < 20.
